Process for preparing phthalocyanines



United States Patent 3,299,093 PROCESS FOR PREPARING PHTHALOCYANINES Luke Ralph Ocone, Wyndmoor, and Burton Peter Block, Wayne, Pa., and Edward George Meloni, Metuchen, N..I., assignors to Pennsalt Chemicals Corporation, Philadelphia, Pa., a corporation of Pennsylvania No Drawing. Filed Mar. 3, 1964, Ser. No. 349,165 1 8 Claims. (Cl. 260-3145) This invention relates to a process for chromium phthalocyanine, whereby improved yields of this coloring material are obtained. More particularly,'the invention pertains to the reaction between phthalonitrile and chromium hexacarbonyl to obtain chromium phthalocyanine.

Chromium (II) phthalocyanine is a known compound which has been described by Elvidge and Lever in J. Chem. Soc., 1961, p. 1257. In the prior art process, chromium triacetate and phthalonitrile are heated at about 270 C. and separated by sublimation techniques. Although the yield of chromium (II) phthalocyanine is not reported, it is obviously small because the product was mixed with by-products which included chrominum (III) phthalocyanines. There is, to date, no efficient process for the preparation of chromium (II) phthalocyanine in good yield and purity.

It has now been found, in accord with this invention, that chromium (II) phthalocyanine is obtained in yields on the order of 40 to 50% and without the formation of troublesome by-products, by reacting chromium hexacarbonyl with phthalonitrile. In the process of the invention, chromium hexacarbonyl is slowly added to phthalonitrile held at a temperature above about 240 C. Conveniently, a solution of chromium hexacarbonyl may be taken into a phthalonitrile solution by an extractive distillation technique whereby the chromium hexacar- 'bonyl solvent distills and extracts more chromium hexacarbonyl and returns with the extract to the reaction mass.

The phthalonitrile reactant is dissolved in an inert high boiling solvent (that is, one which boils above a temperature of about 240 0). Such solvents will include hydrocarbons such as methylnaphthalene and halogenated hydrocarbons such as chloronaphthalene. Also useful are high boiling tertiary amines such as quinoline, etc.

The solvent for the chromium hexacarbonyl appears to have an effect on yield, and preferred solvents are the aliphatic and aromatic hydrocarbons, such as heptane, benzene, and other inert solvents. Somewhat less preferred are the lower aliphatic ethers, such as diethyl ether, diisopropyl ether, dibutyl ether, and the like.

As indicated, in carrying out the preferred process the phthalonitrile is dissolved in the high boiling inert solvent, and brought to reflux. The reaction will preferably be carried out in equipment which will permit the vapors of the chromium hexacarbonyl solvent to condense above the remaining chromium hexacarbonyl. As the vapors condense, the liquid is permitted to fall onto the chromium hexacarbonyl which is extracted and the extract containing hexacarbonyl passes into the reaction flask containing the phthalonitrile reactant. In this way, the carbonyl reactant is uniformly and regularly brought into contact with the phthalonitrile and the reaction proceeds smoothly. When all the chromium hexacarbonyl is dissolved, as seen by physical observation, the refluxing is continued for a short time to insure completion of the reaction and then the reaction mass is filtered under an inert atmosphere using a gas such as argon, nitrogen, etc. to recover the product. The product is a lustrous, dark purple, crystalline, needle-like material which is easily washed with benzene or other solvent, and after drying under nitrogen, is an extremely pure high quality product.

It is essential that the reaction be carried out at temperatures above about 240 C. for when Cr(CO) is extracted into the phthalonitrile solution held at about 180 C. the chromium carbonyl decomposes into metallic chromium, but little or no chromium (II) phthalocyanine is obtained even if the reaction mixture is subsequently heated to 250 C. I

The following examples will serve to further illustrate this invention. Y I

' .-Examplel The reaction is carried out with a continuous infusion extractor (Techniques of Organic Chemistry Interscience Publishers, 1950, page 238, Figure 33) using a fritted glass disc and modified by having a stopcock just below the fritted disc. About 1 g. of Cr(CO) weighed exactly 'by difference is placed on the f-ritted glass disc. With the stopcock closed, 20 ml. of benzene is poured onto the Cr(CO) A Friedrich condenser vented through a mercury bubbler is attached to the top of the extractor apparatus, which is connected to the center neck of a 3- necked flask. One side neck is fitted with a combination nitrogen inlet tube and thermowell. The other is stoppered after a slight excess of phthalonitrile over the stoichiometric amount in m1. of l-chloronapthalene has been added along with a magnetic stirring bar. After the apparatus has been thoroughly purged with nitrogen, the phthalonitrile solution is brought to reflux (252 C.) with stirring While a slow stream of nitrogen is passed through the flask. As refluxing begins, the stopcock in the apparatus is opened slightly to allow the benzene solution to drop into the refluxing solution at such a rate that the temperature remains between 230 and 252 C. The benzene flash distills out, is condensed, and dissolves more Cr(CO) as it returns to the reaction flask through the fritted disc. Refluxing is then continued about thirty minutes beyond the three hours required to dissolve all the Cr(CO) After the reaction mixture cools to room temperature, it is filtered under nitrogen. The lustrous dark purple cystalline needles are washed well with benzene in a nitrogen atmosphere, then sparingly with chloroform and acetone, and finally with several portions of diethyl ether. About a 40% yield is obtained after the product is dried in nitrogen.

Analysis. Calcd. for CrC H N Cr, 9.2%; C, 68.0%; H, 2.8%; N, 19.9%. Found: Cr, 9.4%; C, 68.2%; H, 3.0%; N, 19.6%.

Example II Example I is repeated, except that heptane is used for the CI(CO)6 solvent instead of benzene. The yield of chromium (II) phthalocyanine with this solvent is 48%.

Example III When using diethyl ether as the Cr(CO) solvent, the yield of product is 42%.

Example IV Instead of using benzene in Example I, dibutyl ether is used as the Cr(CO) solvent to obtain chromium (II) phthalocyanine in 38% yield.

Chromium (II) phthalocyanine is easily oxidized, the product containing chromium in the +3 oxidation state. For example, exposure to air of chromium (II) phthalocyanine results in the formation of chromium (III) phthalocyanine hydroxide. Thus, chromium (III) phthalocyanines may be made by using this process to make the chromium (II) phthalocyanine precursor.

It will be understood that numerous variations and changes may be made from the above description and examples without departing from the spirit and scope of the invention.

We claim:

1. A process .for the preparation of chromium (II) phthalocyanine which comprises contacting chromium hexacarbonyl with phthalonitrile at a temperature above about240 C.

2 A- process for preparing chromium (II) phthalocyanine which comprises refluxing a solution of phthalonitrile in an inert solvent boiling above about 240 C., while adding a solution of chromium hexacarbonyl to said phthalonitrile solution.

3. A process for preparing chromium (II) phthalocyanine which comprises refluxing a solution of phthalonitrile in l-chloronaphthalene while adding a hydrocarbon solvent solution of Cr(CO) to said refluxing phthalonitrile solution.

4. The process of claim 3 wherein the hydrocarbon solvent is heptane.

5. The process of claim 3 wherein the hydrocarbon solvent is benzene.

6. A process for preparing chromium (II) phthalocyanine which comprises refluxing a solution of phthalonitrile in an inert solvent boiling above about 240 C., while adding an aliphatic ether solution of chromium hexacarbonyl to said phthalonitrile solution.

7. A process as in claim 6 wherein the phthalonitrile is dissolved in l-chloronaphthalene and the ether is diethyl ether.

8. A process as in claim 6 wherein the phthalonitrile is dissolved in l-chloronaphthalene and the ether is dibutyl ether.

No references cited.

JOHN D. RANDOLPH, Primary Examiner.

J. A. PATTEN, Assistant Examiner. 

1. A PROCESS FOR THE PREPARATION OF CHROMIUM (II) PHTHALOCYANINE WHICH COMPRISES CONTACTING CHROMIUM HEXACARBONYL WITH PHTHALONITRILE AT A TEMPERATURE ABOVE ABOUT 240*C. 